Question

function modifyDatabase(tabla, id, objData, callback, arrayCallback){     $.ajax({         url: 'modifyDatabase.php',         type: 'POST',         dataType: 'json',         data: 'tabla='+tabla+'&id='+id+strData,         success: function(data){                         callback(data);         },     }); }  var obj = {     set: function (data){         alert(this.var1);     },     var1: 100 }  function modifyDatabase('', '', '', obj.set, ''); 

When running this, I get an error message telling me that this.var1 is not set or undefined. If I call the method from somewhere else (not from an asynchronic response) it works fine.

Seems as if the method ‘set’ is not inside ‘obj’.

What is going on?

Answer 1

When you pass a reference to a function this way, it’s actually not passing a reference to the object as well. A quick fix is to create an anonymous function that references the actual object via closures. Here’s a good description of why it didn’t work: http://bitstructures.com/2007/11/javascript-method-callbacks

In short, you need to do:

function modifyDatabase('', '', '', function(){obj.set();}, '');